Debouncer.swift

import Foundation

/// Debouncer is useful for situations like following.
/// If we want to execute action n sec after the last trigger.
public final class Debouncer<T> {
    let dispatchQueue: DispatchQueue
    let interval: TimeInterval
    let action: (T) -> Void

    private var _lastDispatchTime: DispatchTime?

    public init(_ dispatchQueue: DispatchQueue, interval: TimeInterval, action: @escaping (T) -> Void) {
        self.dispatchQueue = dispatchQueue
        self.interval = interval
        self.action = action
    }

    /// Request action to execute.
    public func requestAction(_ dependency: T) {
        let dispatchTime: DispatchTime = .now() + interval
        _lastDispatchTime = dispatchTime
        dispatchQueue.asyncAfter(deadline: dispatchTime) {
            guard self._lastDispatchTime == dispatchTime else {
                // ignore if requested again during interval.
                return
            }
            self.action(dependency)
        }
    }
}

extension Debouncer where T == Void {
    public func requestAction() {
        requestAction(())
    }
}